When you run a pump at 1/4 speed or 15 Hz, how many pumps head will be generated?

The question is interesting I am sure that all friends here know that every pump speed there is different curve for relationships between flow and head Operation of pump at Different speed usually designed from 50% to 100% according to loads required Operating pump@ 25% of its full speed will reduce its discharge head to less than 20% from design pump head and can be known directly by check review new speed curve its new curve easy (without using equation It is nice to mention that in the new ideas for cooling system is using small pump to keep fireon system fine on both condensing unit and evaporator working correctly And stop big pump in case of no loads

Below 15hz (25% max speed) is unlikely to move water out of the mechanical room According to the pump affinity laws, flow is proportional to speed and head is proportional to speed squared. When you run a pump at ¼ speed or 15hz, you can only generate 1/16 of the pumps head. i.e. 1/4 (square) = 1/161/16th of the head is unlikely to even move the water out of the mechanical room.